(a) Field of the Invention
The present invention relates to a resistive component, particularly to a resistive component suitable for detecting electric current and a method of manufacturing the same.
(b) Description of the Related Art
Generally, an electronic device is provided with a resistive component, being a passive component, for detecting electric current. The resistive component suitable for detecting electric current generally has a low resistance value and a low temperature coefficient of resistance (TCR).
A conventional resistive component is disclosed in U.S. Pat. No. 7,238,296, that has a resistive layer be printed on a substrate by a printing technique and then be covered by a glass layer. Its resistance value is adjusted by a laser trimming technique. Finally, the glass layer is covered with a protective layer. The resistive layer is made of an alloy formed by blending Cu—Mn—Ge metallic powders and copper-oxide powders to reduce its resistance value and TCR. Besides glass powders are added into the resistive layer as a binder in order to have better adhesion between the substrate and the resistive layer. However, the glass powders form impurities so that the TCR of the resistive layer cannot be controlled easily. In addition, if the percentage of the glass powders and the copper-oxide powders is too high, such as higher than 10 wt %, the resistance value of the resistive layer is increased and the porous structure forms in the resistive layer. A rather elaborate control of the added quantity of the glass and copper-oxide powders is therefore required during the manufacturing process. The resistive component is required to be sintered in a nitrogen environment at 960° C.˜980° C. in the manufacturing process. The copper in the resistive component, however, is easy to be oxidized which makes the manufacturing process become more difficult.
Another conventional resistive component is disclosed in U.S. Pat. No. 6,771,160, that uses a process like vaporization, sputtering, chemical plating or electroplating deposition to deposit a plurality of resistive layers on a copper foil and then has them be embedded into a printed circuit board (PCB). The resistive layers are made of different alloys or oxides and form a parallel circuit so that the resistive components having different resistance value are manufactured. The use of the vaporization or sputtering deposition process, however, results in high manufacture cost and the process of etching the resistive layers is relatively difficult.